The present invention relates to a multilayer polypropylene film which has been produced by coextrusion and which has improved barrier properties with respect to permeability to water vapor and oxygen and simultaneously possesses favorable slip properties and low shrink values, in order to ensure good machine running properties.
EP-A-0,247,898 (=U.S. Pat. No. 4,921,749) describes a special polypropylene film which is claimed to possess, in particular, high-strength sealed seams and improved barrier properties.
DE-A-35 35 472 (=U.S. Pat. No. 4,786,533) is directed to polypropylene films where a certain amount of resin is incorporated in the base layer. However, the films disclosed therein possess, in particular, inadequate barrier properties towards water vapor, so that there has been a need for films having improved properties in this respect.
DE-A-38 14 942 describes polypropylene films containing a resin proportion of 5 to 40% by weight in their base layers, the resins having a softening point in the range of 80.degree. to 125.degree. C. These films are used as shrink-on labels, but exhibit disadvantages with respect to the barrier properties towards water vapor and oxygen.